This invention relates to a semiconduction injection laser device having a low threshold current and a small change in threshold current due to a variation in temperature.
There have been well known several structures of semiconductor injection lasers in which the threshold current is decreased. Among them a laser structure known as the so-called transverse junction stripe (which is abbreviated to "TJS") laser is particularly excellent. That TJS laser oscillates in the single mode and the characteristics thereof are described in detail, for example, in H. Namizaki article entitled "Transverse-Junction-Stripe Lasers with a GaAs p-n Homojunction," IEEE Journal of Quantum Electronics, QE-11, No. 7, 1975, pages 427-431. However, the TJS laser has been disadvantageous in that a leakage current not contributing to the laser oscillation is increased with an increase in current density and therefor a rise in temperature is attended with a rapid increase in the threshold current until the laser oscillation is ceased due to heat generated therein.
Also U.S. Pat. No. 3,961,996 to H. Namizaki et al. discloses a semiconductor injection laser having a two-dimensional hetero-structure including a double hetero-junction in a direction parallel to that PN homo-junction conducting the laser oscillation and a single hetero-junction in a direction perpendicular to the same PN junction to define an extremely small region by the hetero-junctions which region exhibits the effect of confining carriers and light therein whereby the laser can be operated with a low threshold current. The semiconductor injection laser disclosed in the cited patent has encountered the problems that an increase in temperature causes an abrupt increase in threshold current resulting form a leakage current flowing through a broad area of the junctions.
Accordingly it is a general object of the present invention to improve semiconductor injection laser devices.
It is an object of the present invention to provide a new and improved semiconductor injection laser device having an extremely low leakage current.
It is another object of the present invention to provide a novel semiconductor injection laser device improved in temperature dependency of a leakage current.
It is still another object of the present invention to provide a new and improved semiconductor injection laser device which has a decreased threshold current and a reduced rate of change thereof due to a temperature.